1. Field of the Invention
This invention is directed to combinations of dimercaptothiadiazole-mercaptan coupled dithio compounds with amines which have proven to be highly effective multifunctional antiwear/extreme pressure additives for lubricants and fuels.
2. Description of Related Art
Dimercaptothiadiazole derivatives, such as 2,5-dimercapto-1,3,4-thiadiazole, disodium 2,5-dimercaptothiadiazole, and 2,5-bis(t-nonyl-dithio) thiadiazole, are well known for their antioxidancy, anticorrosion, and metal passivation properties in a variety of lubricant applications, as disclosed in U.S. Pat. Nos. 4,661,273, 4,678,592 and 4,584,114.
Furthermore, U.S. Pat. No. 5,186,850 discloses that the incorporation of the heterocyclic dimercaptothiadiazole functionality into succinimide structures provides ashless dispersants with multifunctional antiwear, antioxidant and corrosion inhibitor properties in lubricant compositions. Additionally, various reaction products of mercapto- and dimercaptothiadiazoles have been known to possess extreme pressure/antiwear properties, in a variety of lubricant formulations, as exemplified in U.S. Pat. Nos. 4,661,273; 4,382,869; and 4,678,592.
The use of amines in lubricants and the detergent industry has been well known for their alkalinity, surface activity, and neutralization capability. Amine phosphate is one class of additives used extensively in industrial oils, and polyamine-derived succinimides are key components in ashless dispersants of engine oils.
Reaction products of dimercaptothiadiazole derived alcohols and alkenyl succininc anhydrides and their subsequent amine reaction products have been found to be effective antiwear/antioxidant additives for lubricants; see U.S. Pat. No. 4,908,144. U.S. Pat. No. 5,188,746 discloses antiwear/antioxidant additives for lubricants based on dimercaptothiadiazole derivatives of acrylate and methacrylate polymers and amine reaction products thereof.
It has now been found that the use of these combinations of thiadiazole-derived dithio additives with amine derivatives, in accordance with the present invention, provide exceptional antiwear/EP activity with significantly enhanced metal passivating/corrosion inhibiting properties for lubricants and fuels.